I think you are dealing with 2 eco-systems here. First, keeping the water in the reservoir at a constant 78 degrees will accelerate root and upper plant development. Here, the aquarium heater is pretty effective.
Now to the upper portion of the IncuTainer. This is where wild fluctuations due to ambient temperature changes from day to night need to be addressed. The aquarium heater will have minor effect on the air temperature around the plant's stem and leaves. So a second heat source like the reptile cage warmer would come into play. Protecting the plant's foliage to maintain a minimum temperature at night to no less than 45 degrees is essential, if you are going to put out your plants early for development in cooler weather.
In summary, I think it best to provide a dual "lower" and "upper" warming solution.
Raybo
